rx function
Implementation
rx(id, [ref, bool unlink = false]) {
if (_rxIds[id] == null) {
_rxIds[id] = [];
}
if (unlink == true) {
// print('removed: ' + id);
_rxIds[id]!.remove(ref);
} else if (ref != null) {
// print('added: ' + id);
_rxIds[id]!.add(ref);
} else {
// print('fetched: ' + id);
}
return _rxIds[id];
}